Refrigeration apparatus condensation prevention means

ABSTRACT

A refrigeration apparatus having wall means defining a chamber to be refrigerated. The chamber is refrigerated at least at times to an above-freezing temperature. A duct for conducting low temperature air is spaced adjacent the wall means of the chamber externally thereof and means are provided for preventing chilling of the wall means by the low temperature duct air to effectively preclude condensation of moisture on the surface thereof confronting the chamber.

United States Patent 1 1 McCullough 1 May 15, 1973 [54] REFRIGERATION APPARATUS [56] References Cited 2Sigg UNITED STATES PATENTS 3,050,956 8/1962 Mann ..62/275 3,287,930 ll/l966 O'Connell"... ....62/l50 [75] Inventor: :"g Evansvme 3,393,530 7/1968 Koch ..62/275 [73] Assignee: Whirlpool Corporation, Benton Har- Primary Exami"e'wmiam Wye bur, Mich Attorney-James S. Nettleton. et al.

[22] Filed: Dec. 1, 1971 [57] ABSTRACT [2]] Appl 203 55 A refrigeration apparatus having wall means defining a chamber to be refrigerated. The chamber is refrigerated at least at times to an above-freezing temperature. A duct for conducting low temperature air is 52 us. Cl. ..62/275 62/80 62/272 Spaced adjacent the means the Chamber [51] Int CL Fzsd 21/06 nally thereof and means are provided for preventing [58'] Field 150 156 chilling of the wall means by the low temperature duct air to effectively preclude condensation of moisture on the surface thereof confronting the chamber.

10 Claims, 5 Drawing Figures PATENTED HAY] 51973 SHEET 1 UF 2 PATENTEU MAY 1 51m SHEET 2 OF 2 REFRIGERATION APPARATUS CONDENSATION PREVENTION MEANS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to refrigeration apparatus and in particular to means for preventing condensation on the chamber wall of a refrigeration apparatus such as a freezer-refrigerator apparatus. A

2. Description of the Prior Art In the Sigl, et al. U. S. Letters Pat. No. 3,411,312, owned by the assignee hereof, a refrigerator with a convertible compartment is disclosed. As shown, ducts are provided for delivering the relatively low temperature refrigerated air from the evaporator to the different compartments. The ducts are disposed behind the rear wall panels defining the different compartments and where the compartment is being maintained as a=refrigerator compartment with the temperature therein being an above-freezing temperature, there is a tendency for moisture to condense on the front surface of the rear wall panel because of the cooling effect of the refrigerated air thereon and the contact thereof by the relatively moist refrigerator compartment air.

It has heretofore been known to heat different portions of the refrigerator wall structures, such as adjacent a movable wall partition, as disclosed in the U. S. Mann et al. Pat. No. 3,027,732; adjacent the door as disclosed in the U. S. Grubbs, Sr. Pat. No. 2,731,804 and U. S. Newill Pat. No. 2,135,091.

SUMMARY OF THE INVENTION The present invention comprehends an improved refrigeration apparatus having wall means defining a chamber, means refrigerating the chamber to an abovefreezing refrigeration temperature, and a duct for conducting air at a temperature lower than the chamber temperature, the duct being spaced adjacent the wall means externally of the chamber, means for preventing undesirable condensation on the surface of the wall means confronting the chamber and on the external surface of the duct, comprising a surface heater disposed intermediate the duct and the wall means for heating the wall means sufficiently to prevent the wall means from being refrigerated by heat exchange with the duct air sufficiently to cause condensation on the wall means of moisture in the air within the chamber.

The invention further comprehends an improved means for effectively eliminating the vexatious problem of condensation as in such a refrigeration apparatus wherein the chamber is at times also refrigerated to a below-freezing temperature. In such a structure, the invention further comprehends the provision of means responsive to the temperature of the chamber air for controlling operation of the heater to provide heating of the wall only when the chamber air temperature is an above-freezing temperature.

The present invention comprehends providing such a surface heater in conjunction with means for directing the heat produced thereby primarily to the chamber wall, while permitting some heat to be transferred to the surface of the air duct. The heater may comprise an electric wire heater carried on a vinyl clad foil and secured to the rear surface of the wall means to be heated in spaced relationship to the duct for improved condensation prevention. The heater may be controlled by a thermostat switch responsive to the temperature of the air in the chamber so that the heater is operated only when the chamber is being utilized as a refrigerator chamber wherein the air is maintained at an abovefreezing temperature conducive to formation of such condensation on the wall and air duct means. Further, the heater may be connected in series with the thermostat switch controlling the refrigerator chamber and in parallel with the compressor and fan motors for improved coordinated functioning therewith.

The heater may be constructed so as to provide a greater heating effect at the lower end thereof than at the upper end thereby to effectively minimize the temperature gradient normally occurring in such a refrigeration chamber. Illustratively, it has been found that in a conventional convertible chamber of this type, when operated as a refrigerator chamber, the temperature between the lower portion and upper portion of the chamber may vary as much as 10 F. By suitably constructing the heater, the temperature variation may be reduced to as small a differential as approximately 2 F.

The wall means may comprise a removable panel at the rear of the chamber which not only overlies the duct to effectively comprise a duct cover, but also to define in combination with the cabinet liner a return air passage for conducting air from the convertible chamber back to the evaporator in the air circulation circuit of the apparatus.

BRIEF DESCRIPTION OF THE DRAWING Other features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing wherein:

FIG. 1 is a front elevation of a refrigeration apparatus having means for effectively minimizing condensation on a wall means of a convertible chamber thereof;

FIG. 2 is a fragmentary enlarged front elevation thereof with portions broken away to facilitate illustration of the invention;

FIG. 3 is a vertical section thereof taken substantially along the line 3-3 of FIG. 2;

FIG. 4 is a horizontal section taken substantially along the line 4-4 of FIG. 2; and

FIG. 5 is a schematic diagram of a portion of the control circuit illustrating the control of the heater in coordination with the compressor and fan of the refrigeration apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the exemplary embodiment of the invention as disclosed in the drawing, a refrigeration apparatus generally designated 10 is shown to comprise a cabinet 11 defining a refrigerator chamber 12, a convertible chamber 13, and a freezer chamber 14. The cabinet includes side walls 15 and 16, an upright center wall 17 and a horizontal divider wall 18 cooperatively defining the different chambers. The chambers are refrigerated by means of refrigerated air delivered thereto from an evaporator 19 by an air moving means, herein illustratively comprising fan 20. Thus, air is delivered to the freezer chamber 14 through an outlet 21 in the rear wall 22 of the freezer chamber 14. Refrigerated air is delivered to the convertible chamber 13 through an outlet 23 in the rear liner 24 of the convertible chamber 13 and air is delivered through an outlet 25 in the rear liner 26 of refrigerator chamber 13. Suitable control means 270 and 27b are provided for controlling the air flow to chambers 12 and 13 for selectively controlling the temperature in the chambers 12 and 13 respectively, and more specifically for selectively causing the temperature in chamber 13 to be a below-freezing temperature whereby chamber 13 comprises a freezer chamber, or an above-freezing temperature whereby chamber 13 comprises a refrigerator compartment. Air is returned to the evaporator from refrigerator chamber 12 through an outlet passage 28, from freezer compartment 14 through an outlet 29, and from convertible chamber 13 through an outlet 30. Outlet 30 herein comprises a plurality of openings in a duct cover 31 defining the wall means at the rear of chamber 13.

When chamber 13 is maintained at an above-freezing temperature, the air therein is relatively moist. As shown in FIG. 4, the rear wall means 31 defines a vertical space 34 forwardly of the rear liner 24 and through which the supply duct 32 extends for supplying refrigerated air from fan 20 to the outlets 23 and 25. The air in duct 32 is relatively cold, i.e., at a below-freezing temperature such as approximately and thus heat exchange between the duct and duct cover wall 31 would tend to cool the duct cover 31 to below the temperature thereof when the chamber 13 is being maintained at an above-freezing temperature as a refrigerator chamber. Under these conditions, moisture would tend to condense on the front surface 33 of the duct cover 31 and on the external surface of duct 32, presenting an undesirable condition. The present invention comprehends means for eliminating this undesirable condition in a novel and simple manner.

More specifically, the invention comprehends providing in the space 34 between the duct 32 and the wall means, or duct cover, 31, a heater 35 which comprises a surface heater extending over substantially the entire rear surface 36 of the duct cover for effectively heating the duct cover sufficiently to prevent condensation of moisture thereon as a result of heat exchange of the duct cover with duct 32. As shown in FIG. 4, the heater 35 comprises a serpentine electric wire heater having terminals 37 at the upper end of the duct cover and controlled by thermostat switch 38 disposed within space 34 above the outlet openings 30. The switch 38 comprises a manually adjustable bimetal switch permitting the heater 35 to be energized only when the temperature in the convertible chamber 13 is an abovefreezing temperature indicative of the operation of the chamber as a refrigerator chamber.

The heater may include an upward extension 39 for heat transfer association with the control 27b so as to prevent false operation of the control as by undesirable cooling of the bellows element thereof below the tem perature sensed by the sensing element thereof.

Further as shown in FIG. 2, the turns of the heater 35 are nonuniformly disposed so as to provide a greater heating effect at the lower end 40 of the duct cover as compared to the heating effect provided at the upper end 41 thereof. The configuration of the heater is preselected to cause a sufficient difference in the heating effect to counterbalance the normal temperature gradient in the chamber 13 when it is being used as a refrigerator chamber so as to provide effectively uniform cooling effect throughout the vertical extent thereof. Thus, illustratively, it has been found that in such a conventional convertible chamber, a temperature variation of as much as F. may exist between the lower portion and upper portion thereof because of the natrual tendency of cool air to settle. By means of the illustrated heater configuration, the temperature differential may be caused to be effectively minimized so as to be no more than approximately 2 F.

Duct cover wall 31 comprises a U-section element having rearwardly turned side wall portions 42 and 43, each terminating respectively in outturned distal ends 44 and 45 provided with slots 46 permitting the duct cover to be secured to the liner 24 by suitable removable fastening means, such as screws 47. Thus, the duct cover wall portion 42 is closely juxtaposed to the dividing wall 17 of the cabinet which, by virtue of the refrigeration of chamber 12, would tend to be maintained at a temperature whereat condensation would occur on the outer surface thereof. The provision of heater wire portions 48 on the inner surface of the wall portion 42 effectively precludes such condensation thereon. The other turned wall 43 is juxtaposed to the lefthand side wall 15 of the refrigerator cabinet and thus is relatively warm so as to effectively obviate the need for the heater wire means on this portion of the duct cover.

As further shown in FIG. 2 of the drawing, the turns of the heater not only are more closely spaced at the bottom portion of the duct cover, illustratively at turns 35a, but the turns 35b defining the upper portion of the heater may have different lengths to provide the desired temperature gradient compensation functioning discussed above. The control switch 38 may be mounted on the side wall 43, as shown in FIG. 4, to be spaced from the relatively short turns of the heater, as shown in FIG. 2, so as to more accurately reflect the temperature of the air of compartment 13 as a result of the juxtaposition of the switch to the outlet openings 30.

As shown in FIG. 5, the control switch 38 may be connected in parallel with the compressor motor 49 and the motor 50 driving fan 20, and in series with the conventional thermostat switch 51 for controlling the operating temperature of the reflector as a portion of control 27.

As shown in FIG. 4, the heater 35 is affixed to the front vinyl surface 52 of a vinyl clad metal foil sheet 53 so that the metal foil 54 thereof is disposed between the heater and the duct 32 thereby to reflect most of the heat back to the heater and duct cover 31 yet allowing asufficient amount of heat to reach the duct to prevent condensation on the outer surface thereof. The duct is constructed constructed of a material which prevents any significant warming of the air in the duct. The assembled heater and vinyl clad foil sheet may be secured to the rear of the duct cover by any suitable means, such as masking tape strips 55. The heater thusly is carried by the duct cover and is preferably spaced slightly from the duct within space 34, as shown in FIG. 4.

The lower end of the duct cover effectively defines the return passage for conducting air from compartment 13 back to the evaporator through a suitable opening 56in the horizontal dividing wall 18. The proximity of the lower heater turns 35a to the dividing wall 18 further provides some heating thereof to minimize condensation on the dividing wall as well as on the duct cover.

The foregoing disclosure of specific embodiments is illustrative of the broad inventive concepts comprehended by the invention.

Having described the invention, the embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: I

1. In a refrigeration apparatus having wall means defining a chamber, means refrigerating said chamber to an above-freezing refrigerating temperature, and a duct for conducting air at a temperature lower than said refrigerating temperature, said duct being spaced adjacent said wall means externally of said chamber,

-means for preventing undesirable condensation on the surface of said wall means confronting said chamber comprising:

a surface heater disposed next to said wall means intermediate said duct and said wall means for heating said wall means sufficiently to prevent said wall means from being refrigerated by heat exchange with said duct air sufficiently to cause condensation on said wall means of moisture in the air within said chamber.

2. The refrigeration apparatus means of claim 1 wherein said heater is constructed to provide heating of said wall means at the lower end of the heater greater than the heating thereof at the upper end of the heater to effectively minimize vertical temperature gradient within said chamber.

3. The refrigeration apparatus means of claim 1 wherein said heater is carried by said wall means.

4. The refrigeration apparatus means of claim 1 wherein means are provided between said heater and said duct for reflecting heat energy from said heater back toward said wall means while permitting a portion of said heat energy to heat said duct to prevent condensation thereon.

5. The refrigeration apparatus means of claim 1 wherein said wall means comprises a removable panel forwardly overlying said duct, said heater being secured to the rear surface of said panel.

6. The refrigeration apparatus means of claim 1 wherein said wall means defines a return air duct for returning air from said chamber for re-cooling thereof.

7. In a refrigeration apparatus having wall means defining a chamber, means refrigerating said chamber to an above-freezing refrigerating temperature, and a duct for conducting air at a temperature lower than said refrigerating temperature, said duct being spaced adjacent said wall means externally of said chamber, means for preventing undesirable condensation on the surface of said wall means confronting said chamber comprising:

a surface heater disposed next to said wall means in termediate said duct and said wall means for heating said wall means sufficiently to prevent said wall means from being refrigerated by heat exchange with said duct air sufficiently to cause condensation on said wall means of moisture in the air within said chamber;

means for selectively causing the refrigerating means to refrigerate said chamber to a below-freezing temperature; and

control means responsive to the temperature of the chamber air for controlling operation of the heater to provide heating of said wall only when the chamber air temperature is an above-freezing temperature.

8. The refrigeration apparatus means of claim 7 wherein said heater is constructed to provide heating of said wall means at the lower end of the heater greater than the heating thereof at the upper end of the heater to effectively minimize vertical temperature gradient within said chamber.

9. The refrigeration apparatus means of claim 7 wherein said refrigerating means includes an air moving means driven by an electric motor, said heater comprises an electric heater, and said control means comprises a switch connecting said heater in parallel with said motor.

10. The refrigeration apparatus means of claim 7 wherein said refrigerating means includes an air moving means driven by an electric motor and a thermostat switch for causing operation of the fan means whenever the temperature in the chamber rises above a preselected temperature, said heater comprises an electric heater, and said control means comprises a switch connecting said heater in parallel with said motor and in series with said thermostat switch. 

1. In a refrigeration apparatus having wall means defining a chamber, means refrigerating said chamber to an above-freezing refrigerating temperature, and a duct for conducting air at a temperature lower than said refrigerating temperature, said duct being spaced adjacent said wall means externally of said chamber, means for preventing undesirable condensation on the surface of said wall means confronting said chamber comprising: a surface heater disposed next to said wall means intermediate said duct and said wall means for heating said wall means sufficiently to prevent said wall means from being refrigerated by heat exchange with said duct air sufficiently to cause condensation on said wall means of moisture in the air within said chamber.
 2. The refrigeration apparatus means of claim 1 wherein said heater is constructed to provide heating of said wall means at the lower end of the heater greater than the heating thereof at the upper end of the heater to effectively minimize vertical temperature gradient within said chamber.
 3. The refrigeration apparatus means of claim 1 wherein said heater is carried by said wall means.
 4. The refrigeration apparatus means of claim 1 wherein means are provided between said heater and said duct for reflecting heat energy from said heater back toward said wall means wHile permitting a portion of said heat energy to heat said duct to prevent condensation thereon.
 5. The refrigeration apparatus means of claim 1 wherein said wall means comprises a removable panel forwardly overlying said duct, said heater being secured to the rear surface of said panel.
 6. The refrigeration apparatus means of claim 1 wherein said wall means defines a return air duct for returning air from said chamber for re-cooling thereof.
 7. In a refrigeration apparatus having wall means defining a chamber, means refrigerating said chamber to an above-freezing refrigerating temperature, and a duct for conducting air at a temperature lower than said refrigerating temperature, said duct being spaced adjacent said wall means externally of said chamber, means for preventing undesirable condensation on the surface of said wall means confronting said chamber comprising: a surface heater disposed next to said wall means intermediate said duct and said wall means for heating said wall means sufficiently to prevent said wall means from being refrigerated by heat exchange with said duct air sufficiently to cause condensation on said wall means of moisture in the air within said chamber; means for selectively causing the refrigerating means to refrigerate said chamber to a below-freezing temperature; and control means responsive to the temperature of the chamber air for controlling operation of the heater to provide heating of said wall only when the chamber air temperature is an above-freezing temperature.
 8. The refrigeration apparatus means of claim 7 wherein said heater is constructed to provide heating of said wall means at the lower end of the heater greater than the heating thereof at the upper end of the heater to effectively minimize vertical temperature gradient within said chamber.
 9. The refrigeration apparatus means of claim 7 wherein said refrigerating means includes an air moving means driven by an electric motor, said heater comprises an electric heater, and said control means comprises a switch connecting said heater in parallel with said motor.
 10. The refrigeration apparatus means of claim 7 wherein said refrigerating means includes an air moving means driven by an electric motor and a thermostat switch for causing operation of the fan means whenever the temperature in the chamber rises above a preselected temperature, said heater comprises an electric heater, and said control means comprises a switch connecting said heater in parallel with said motor and in series with said thermostat switch. 